Gravity Ultrafiltration at the Household Tap: Flux Decline, the Backwash Budget, Net Yield, and Storage After a Residual-Free Barrier

SIMULATED, NOT MEASURED. A gravity ultrafiltration unit is modelled over its fouling life: backwash consumes 1.1% of gross production, net life yield is 5815 L over 167 days at US$15.993 per 1000 L, and the residual-free product is bound to one-day tap-dispensed storage with a first-draw rule. Nothing was built or field-tested.